What is the most appropriate next test for a 55-year-old patient with exertional chest pain, hypercholesterolemia (elevated total cholesterol), a high-density lipoprotein (HDL) level of 55, a cardiovascular disease (CVD) risk score of 5.6%, and a left bundle branch block (LBBB) on electrocardiogram (EKG)?

Diagnostic Approach for a 55-Year-Old with Exertional Chest Pain and LBBB

For a 55-year-old patient with exertional chest pain, elevated total cholesterol, HDL of 55, CVD risk score of 5.6%, and left bundle branch block (LBBB) on EKG, coronary CT angiography (CCTA) should be ordered as the next diagnostic test.

Rationale for CCTA as First-Line Test

The presence of LBBB significantly complicates the diagnostic approach for coronary artery disease (CAD) evaluation. Standard exercise ECG testing has several important limitations in this setting:

• Exercise ECG has poor diagnostic accuracy (36-60%) and low specificity (33%) in patients with LBBB 1
• LBBB creates baseline ECG abnormalities that interfere with accurate interpretation of stress-induced changes 2
• Exercise stress can produce false-positive results due to septal perfusion defects even in the absence of coronary disease 1

CCTA offers significant advantages in this clinical scenario:

• High sensitivity (95-99%) for detecting obstructive coronary artery disease 1, 3
• Direct anatomical visualization of coronary arteries 1
• Particularly beneficial for patients with intermediate pre-test probability of CAD, which applies to this patient with a CVD risk score of 5.6% 1
• High negative predictive value for ruling out obstructive coronary disease 1

Alternative Testing Options and Their Limitations

Exercise Stress Test

• Not recommended as first-line due to poor diagnostic accuracy in LBBB 2, 1
• Low sensitivity (45-50%) compared to imaging-based tests 2

Vasodilator Stress Testing

• If CCTA is unavailable, vasodilator (adenosine, dipyridamole, regadenoson) stress myocardial perfusion imaging would be the preferred alternative 2, 1
• Higher sensitivity (90-91%) and specificity (84%) compared to exercise testing in LBBB patients 2, 1

BNP/Troponin Levels

• Not indicated as the next test in stable chest pain evaluation with LBBB
• More appropriate for acute presentations or heart failure evaluation

Coronary Angiography

• Too invasive as an initial diagnostic test for stable symptoms 1, 3
• Should be reserved for patients with high pre-test probability or after non-invasive testing suggests significant CAD 1

Clinical Decision Algorithm

1. First-line test: Coronary CT angiography

   • If negative → Consider other causes of chest pain
   • If non-obstructive CAD → Consider medical management
   • If obstructive CAD → Consider functional testing or direct referral for invasive angiography

2. If CCTA contraindicated or unavailable: Vasodilator stress myocardial perfusion imaging

   • Adenosine, dipyridamole, or regadenoson preferred over dobutamine in LBBB 2, 1

3. If significant CAD identified: Proceed to invasive coronary angiography for potential intervention

Important Considerations

• The patient's intermediate CVD risk score (5.6%) places them in a range where CCTA is most cost-effective 3
• The presence of LBBB may indicate underlying structural heart disease, making anatomical assessment particularly valuable 1
• The patient's relatively good HDL level (55) is a positive prognostic factor, as low HDL is associated with endothelial dysfunction and higher risk coronary anatomy 4, 5
• CCTA provides comprehensive assessment of plaque location, severity, and composition, which helps in risk stratification 4

By following this approach, you can effectively evaluate this patient's chest pain while avoiding the diagnostic pitfalls associated with LBBB on standard exercise testing.